Surface planarization processes for the fabrication of magnetic heads and semiconductor devices

ABSTRACT

Surface planarization processes for the fabrication of magnetic heads and semiconductor devices are described herein. In one illustrative example, magnetic structures are formed over a substrate and insulator materials are deposited over and around the magnetic structures. A chemical mechanical polishing (CMP) is performed to remove top portions of the insulator materials and to expose the tops of the magnetic structures, such that the tops of the magnetic and insulator materials form a top surface. Due to the different CMP removal rates of the materials, small surface “steps” are formed along the top surface between the materials. To eliminate or reduce these steps, polymer materials (e.g. polystyrene or PMMA) are formed to selectively bond with the tops of the insulator materials to a sufficient thickness so that a substantially planar top surface is formed with tops of the magnetic materials. This may be done by applying a polymer initiator to selectively bond with the tops of the insulator materials and subsequently performing a polymerization process. Alternatively, the polymer materials may be formed by applying a polymer solution to the structure.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates generally to surface planarization processes forthe fabrication of magnetic heads and other devices (such assemiconductor devices), and more particularly to processes thateliminate or reduce surface “steps” formed between different materialsby selectively bonding polymer materials to one of the materials.

2. Description of the Related Art

A write head is typically combined with a magnetoresistive (MR) or giantmagnetoresistive (GMR) read head to form a merged head, certain elementsof which are exposed at an air bearing surface (ABS). The write head ismade of first and second pole pieces having first and second pole tips,respectively, which terminate at the ABS. The first and second polepieces are connected at the back gap by a yoke, whereas the first andsecond pole tips are separated by a non-magnetic gap layer. Aninsulation stack, which comprises a plurality of insulation layers, issandwiched between the first and second pole pieces, and a coil layer isembedded in this insulation stack. A processing circuit is connected tothe coil layer for conducting write current through the coil layerwhich, in turn, induces write fields in the first and second polepieces. Thus, write fields of the first and second pole tips at the ABSfringe across the gap layer. In a magnetic disk drive, a magnetic diskis rotated adjacent to, and a short distance (fly height) from, the ABSso that the write fields magnetize the disk along circular tracks. Thewritten circular tracks then contain information in the form ofmagnetized segments with fields detectable by the read head.

One or more merged heads may be employed in a magnetic disk drive forreading and writing information on circular tracks of a rotating disk Amerged head is mounted on a slider that is carried on a suspension. Thesuspension is mounted to an actuator which rotates the magnetic head tolocations corresponding to desired tracks. As the disk rotates, an airlayer (an “air bearing”) is generated between the rotating disk and anair bearing surface (ABS) of the slider. A force of the air bearingagainst the air bearing surface is opposed by an opposite loading forceof the suspension, causing the magnetic head to be suspended a slightdistance (flying height) from the surface of the disk.

Improved methods for making magnetic heads have become increasinglyimportant for proper head fabrication and performance. Magnetic headassemblies are typically made of multiple thin film layers which arepatterned to form various shaped layers in the head. Some of the layersare electroplated, while other layers are sputter deposited on a wafersubstrate. Photolithography processes are typically utilized to createvery small track widths for the magnetic heads, resulting in increasedstorage capacity in magnetic disks.

During a photolithography process, a mask image or pattern which definesthe various components is focused onto a photosensitive layer usingultraviolet light The image is focused onto the surface using an opticaldevice of a photolithography tool, and is imprinted into thephotosensitive layer. To build increasingly smaller structures,increasingly fine images must be focused onto the surface of thephotosensitive layer (i.e., the optical resolution must increase). Asoptical resolution is increased, the depth of focus of the mask image iscorrespondingly narrowed due to the narrow range in depth of focusimposed by the high numerical aperture lenses in the photolithographytool. This narrowing depth of focus is often the limiting factor in thedegree of resolution obtainable (and thus the smallest structuresobtainable) using the photolithography tool. The extreme topography(i.e., the “hills” and “valleys” along the surfaces) exaggerates theeffects of decreasing depth of focus. Thus, in order to properly focusthe mask image defining sub-micron geometries onto the photosensitivelayer, a precisely flat surface is desired. A precisely flat (i.e. fullyplanarized) surface will allow for extremely small depths of focus and,in turn, allow the definition and subsequent fabrication of extremelysmall structures.

Typically, a chemical mechanical polishing (CMP) is utilized as themeans of reducing the topography in order to achieve adequate criticaldimension (CD) control. CMP involves removing at least a portion of asacrificial layer of dielectric material using mechanical contactbetween the wafer and a moving polishing pad saturated with slurry.Polishing flattens out most height differences, since high areas oftopography (“hills”) are removed faster than areas of low topography(“valleys”). Such polishing is the only technique with the capability ofsmoothing out topography over millimeter scale planarization distances.

When two or more different materials form the top surface, however,surface “steps” may remain between the materials even after CMP. It hasbeen observed that, after the CMP process in magnetic headmanufacturing, surface steps in the range of 10–300 nm remain betweenthe materials. One surface material may be a metal and the othermaterial may be a dielectric; these materials have very different CMPremoval rates. This non-ideal situation adversely affects subsequentprocessing steps (e.g. photolithography steps). A non-planar surfacechanges the thickness distribution of the subsequently depositedmaterials and increases the chance that surface scattering will occur.

FIG. 1 is the first in a series of illustrations of FIGS. 1–3 whichdescribes in more detail the problem of conventionally forming a planarsurface using a CMP process. An initial structure 100 includes asubstrate 102 having a plurality of first material structures 104. Inthis example, first material structures 104 include structures 106, 108,and 110. Since structures 106, 108, and 110 cover only portions ofsubstrate 102, recesses (such as recesses 112 and 114) are formedbetween structures 106, 108, and 110 and the exposed portions ofsubstrate 102. In the fabrication of magnetic heads, substrate 102 istypically a metal or a magnetic material (such as a pole piece layer ofa magnetic head) or alternatively a non-magnetic material or aninsulator. First deposited material 104 is typically a metal or amagnetic material (such as a pedestal of the pole piece).

It is desired to fill in the recesses with a material (e.g. aninsulator) in an attempt to form a top planar surface with the tops ofstructures 106, 108, and 110. This is done so that another material(e.g. a metal or a magnetic material) can be deposited over the surfaceand contact can be made with it and the tops of the first materialstructures 104. To illustrate, it is shown in FIG. 2 that a secondmaterial 202 is deposited over and around these first materialstructures 104. Second material 202 may be an insulator, such as alumina(Al₂O₃). In FIG. 3, it is shown that a chemical mechanical polishing(CMP) is performed over the structure to remove top surface portions ofsecond material 202 such that the tops of first material structures 104are exposed and a top surface is formed from the tops of first andsecond materials 104 and 202.

The top surface formed from the tops of first and second materials 104and 202 is somewhat flat Since first and second materials 104 and 202have different CMP removal rates, however, small surface “steps” betweenthese materials remain along the top surface even after the CMP (i.e.,the resulting top surface is not entirely coplanar). The surface stepsbetween first and second materials 104 and 202 (such as a step 310) maybe, for example, in the range of about 10–300 nm. Again, this non-idealsituation adversely affects subsequent processing steps (e.g.photolithography steps) during the formation of the magnetic head.

Accordingly, what are needed are improved surface planarizationprocesses for the fabrication of magnetic heads or other devices such assemiconductor devices.

SUMMARY OF THE INVENTION

Surface planarization methods for the fabrication of magnetic heads andother devices in order to achieve good critical dimension (CD) controlare described herein. In one illustrative embodiment, magneticstructures are formed over a substrate and insulator materials aredeposited over and around the magnetic structures. A chemical mechanicalpolishing (CMP) is performed to remove top portions of the insulatormaterials and to expose the tops of the magnetic structures such thatthe tops of the magnetic and insulator materials form a top surface. Dueto the different CMP removal rates of the materials, however, smallsurface “steps” remain between the different materials after the CMP.

According to the invention, polymer materials (e.g. polystyrene or PMMA)are formed to selectively bond with the top of the insulator materials.The polymer materials are formed to a thickness sufficient such that thetops of the polymer and magnetic materials form a substantially planartop surface. The polymer materials may be formed by applying a polymerinitiator layer to create a bond with the top of the insulator materialsand subsequently performing a polymerization process. Alternatively, thepolymer materials may be formed by applying a polymer solution to thestructure.

Since the surface steps between these different materials are eliminatedor substantially reduced to form substantially planar top surfaces, goodcritical dimension (CD) control in photolithography processes can beachieved.

BRIEF DESCRIPTION OF THE DRAWINGS

For a fuller understanding of the nature and advantages of the presentinvention, as well as the preferred mode of use, reference should bemade to the following detailed description read in conjunction with theaccompanying drawings:

FIG. 1 is the first in a series of illustrations of FIGS. 1–3 whichdescribe the problem of conventional surface planarization processeswhich utilize chemical mechanical polishing (CMP), showing moreparticularly a substrate having magnetic structures formed thereon;

FIG. 2 is the second in a series of illustrations of FIGS. 1–3 whichdescribe the problem of conventional surface planarization processes,showing more particularly insulator materials deposited over themagnetic structures;

FIG. 3 is the third in a series of illustrations of FIGS. 1–3 whichdescribe the problem of conventional surface planarization, showing moreparticularly the resulting structure after a CMP where small surfacesteps remain between the magnetic structures and insulator materials;

FIG. 4 is a planar view of a conventional magnetic disk drive;

FIG. 5 is an end view of a slider with a magnetic head of the disk driveas seen in plane II—II of FIG. 4;

FIG. 6 is an elevation view of the magnetic disk drive wherein multipledisks and magnetic heads are employed;

FIG. 7 is an isometric illustration of an exemplary suspension systemfor supporting the slider and magnetic head;

FIG. 8 is a partial elevation view of the slider and magnetic head asseen in plane V—V of FIG. 5;

FIG. 9 is a top view of the second pole piece and coil layer, a portionof which is shown in FIG. 5, with all insulation material removed;

FIG. 10 is a partial ABS view of the slider taken along plane VII—VII ofFIG. 8 to show the read and write elements of the magnetic head;

FIG. 11 is the first in a series of five illustrations of FIGS. 11–15which describe a surface planarization process of the present invention,showing more particularly a substrate having magnetic structures formedthereon;

FIG. 12 is the second in a series of five illustrations of FIGS. 11–15which describe the surface planarization process of the presentinvention, showing more particularly an insulator material depositedover the magnetic structures;

FIG. 13 is the third in a series of five illustrations of FIGS. 11–15which describe the surface planarization process of the presentinvention, showing more particularly the resulting structure after a CMPwhere small surface steps remain between the magnetic structures and theinsulator materials;

FIG. 14 is the fourth in a series of five illustrations of FIGS. 11–15which describe the surface planarization process of the presentinvention, showing more particularly a polymer initiator layerselectively bonded with the tops of the insulator materials;

FIG. 15 is the fifth and final illustration of a series of fiveillustrations of FIGS. 11–15 which describe the surface planarizationprocess of the present invention, showing more particularly a polymerlayer formed with the tops of the insulator materials to a thicknesssufficient such that a substantially planar top surface is formed withit and the magnetic structures;

FIG. 16 is the first in a series of four illustrations of FIGS. 16–19which describe another surface planarization process of the presentinvention, showing more particularly a substrate having magneticstructures formed thereon;

FIG. 17 is the second in a series of four illustrations of FIGS. 16–19which describe the other surface planarization process of the presentinvention, showing more particularly an insulator material depositedover the magnetic structures;

FIG. 18 is the third in a series of four illustrations of FIGS. 16–19which describe the other surface planarization process of the presentinvention, showing more particularly the resulting structure after a CMPwhere small surface steps remain between the magnetic structures and theinsulator materials;

FIG. 19 is the fourth and final illustration of a series of fourillustrations of FIGS. 16–19 which describe the other surfaceplanarization process of the present invention, showing moreparticularly a polymer layer formed with the tops of the insulatormaterials to a thickness sufficient such that a substantially planar topsurface is formed with it and the magnetic structures;

FIG. 20 is the first in a series of three illustrations of FIGS. 20–22which describe even another surface planarization process of the presentinvention, showing more particularly a substrate having magneticstructures formed thereon;

FIG. 21 is the second in a series of three illustrations of FIGS. 20–22which describe this other surface planarization process of the presentinvention, showing more particularly a polymer initiator layerselectively bonded with the tops of the insulator materials; and

FIG. 22 is the third and final in a series of three illustrations ofFIGS. 20–22 which describe the surface planarization process of thepresent invention, showing more particularly a polymer layer formed withthe tops of the insulator materials to a thickness sufficient such thata substantially planar top surface is formed with it and the magneticstructures.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

The following description is the best embodiment presently contemplatedfor carrying out the present invention. This description is made for thepurpose of illustrating the general principles of the present inventionand is not meant to limit the inventive concepts claimed herein.

Referring now to the drawings, wherein like reference numerals designatelike or similar parts throughout the several views, there is illustratedin FIGS. 4–6 a conventional magnetic disk drive 30. The drive 30includes a spindle 32 that supports and rotates a magnetic disk 34. Thespindle 32 is rotated by a motor 36 that, in turn, is controlled by amotor controller 38. A horizontal combined magnetic head 40 for readingand recording is mounted on a slider 42. The slider 42 is supported by asuspension 44 and actuator arm 46. A plurality of disks, sliders andsuspensions may be employed in a large capacity direct access storagedevice (DASD), as shown in FIG. 6. The suspension 44 and actuator arm 46position the slider 42 to locate the magnetic head 40 in a transducingrelationship with a surface of the magnetic disk 34. When the disk 34 isrotated by the motor 36, the slider is supported on a thin (typically,0.05 μm) cushion of air (air bearing) between the disk and an airbearing surface (ABS) 48.

The magnetic head 40 may be employed for writing information to multiplecircular tracks on the surface of the disk 34, as well as for readinginformation therefrom. Processing circuitry 50 exchanges signalsrepresenting such information with the head 40, provides motor drivesignals, and also provides control signals for moving the slider 42 tovarious tracks. In FIGS. 4 and 7 the slider 42 is shown mounted to ahead gimbal assembly (HGA) 52 that is mounted to the suspension 44. Allof the above components are supported on a base 53.

FIG. 8 is a side cross-sectional elevation view of a conventionalmagnetic head 40 having a write head portion 54 and a read head portion56. The read head portion includes a read sensor 58. The read sensor 58is sandwiched between first and second gap layers 60 and 62 that are, inturn, sandwiched between first and second shield layers 64 and 66. Inresponse to external magnetic fields, the resistance of the read sensor58 changes. A sense current conducted through the sensor causes theseresistance changes to be manifested as potential changes, which areprocessed by the processing circuitry 50 shown in FIG. 6.

The write head portion 54 of the head includes a coil layer 68sandwiched between first and second insulation layers 70 and 72. A thirdinsulation layer 74 may be employed for planarizing the head toeliminate ripples in the second insulation layer caused by the coillayer 68. The first, second and third insulation layers are referred toas an “insulation stack”. The coil layer 68, and the first, second andthird insulation layers 70, 72 and 74, are sandwiched between first andsecond pole piece layers 76 and 78. The first and second pole piecelayers 76 and 78 are magnetically connected at a back gap 80, and havefirst and second pole tips 82 and 84 that are separated by anon-magnetic gap layer 86 at the ABS. As shown in FIGS. 5 and 7,conductive pads 88, 90, 100, and 102 connect leads from the read sensor58 and leads 104 and 106 from coil 68 (see FIG. 9) to leads 96, 98, 108,and 110 on the suspension 44.

FIGS. 11–15 are cross-sectional views of partially constructed magneticheads for describing a surface planarization method of the presentinvention. The method of FIGS. 11–15 may be utilized for making amagnetic head in the disk drive described above in relation to FIGS.4–10. This magnetic head will have a unique structure as shown anddescribed later in relation to FIG. 15.

An initial substrate structure 1100 includes a substrate 1102 having aplurality of first material structures 1104 formed thereon. In thisexample, first material structures 1104 include structures 1106, 1108,and 1110. Since structures 1106, 1108, and 1110 cover only portions ofsubstrate 1102, recesses (such as recesses 1112 and 1114) are formedbetween structures 1106, 1108, and 1110 and the exposed portions ofsubstrate 1102. In the fabrication of magnetic heads, substrate 1102 istypically a metal and/or a magnetic material (such as a pole piece layerof a magnetic head), whereas first deposited material 1104 is typicallya metal and/or a magnetic material (such as a pedestal of the polepiece). The magnetic material may include nickel-iron (NiFe) orcobalt-iron (CoFe).

It is desired to fill in these recesses with a material (e.g. aninsulator) in an attempt to form a top planar surface with the tops ofstructures 1106, 1108, and 1110. This is done so that another material(e.g. a metal or a magnetic material) can be deposited over the flatsurface and contact can be made (i.e. physical, electrical, and/ormagnetic contact) with it and the tops of the first material structures1104.

To illustrate, it is shown in FIG. 12 that a second material 1202 isdeposited over and around these first material structures 1104. Secondmaterial 1202 may be an insulator, such as alumina (Al₂O₃). In FIG. 13,it is shown that a chemical mechanical polishing (CMP) is then performedover the structure to remove top surface portions of second material1202 such that the tops of first material structures 1104 are exposedand a top surface (which is somewhat flat) is formed from the tops offirst and second materials 1104 and 1202. However, small surface stepsremain between first and second materials 1104 and 1202 along the topsurface even after the CMP (i.e., the resulting top surface is notentirely coplanar). Steps remain between the materials because they havedifferent CMP removal rates. These surface steps may be, for example, inthe range of about 10–300 nm. If no other processes are utilized toreduce the size of these steps, the non-ideal situation adverselyaffects subsequent processing steps (e.g. photolithography steps) asdescribed earlier.

In FIG. 14, it is shown that a polymer initiator layer 1402 (or polymerstarter) is applied and selectively absorbed only by the top surfaces ofsecond material 1302 (i.e. the insulator). Thus, a chemical bond isformed between the tops of second material 1302 and polymer initiatorlayer 1402. In contrast, little or no absorption or bonding occursbetween the polymer initiator and the top surfaces of first materialstructures 1104. Polymer initiator layer 1402 may be, for example,Azomonochlorsilane (AMCS) where a resulting silane bond is formedbetween the tops of second material 1302 and polymer initiator layer1402. As another example, polymer initiator layer 1402 may beAzo-Thiol-Initiator where a resulting thiol bond is formed between thetops of second material 1302 and polymer initiator layer 1402. Polymerinitiator layer 1402 may be a monomolecular layer having a thickness ofone to a few nanometers (nm). The polymer starter may be applied to thestructure by dipping or floating over.

In FIG. 15, it is shown that a polymerization process is then utilizedto form polymer layers 1502 over the tops of second materials 1302.Preferably, polymer layers 1502 are formed to a thickness sufficient toreach the height of the tops of first material structures 1104. That is,the process is preferably employed such that polymer layers 1502 andfirst material structures 1104 form a substantially planar top surface.In the present embodiment, polymer layers 1502 have a thickness ofbetween about 10–300 nm depending on the exact materials utilized.

Polymers are well-known in the art and may be any one of numerousnatural or synthetic compounds of high molecular weight having a numberof repeated linked molecules. Typically, a polymer has a molecularweight of several thousands or more (even hundreds of thousands ormillions), and thus has large intermolecular forces, entangled molecularchains, and moves more slowly than small molecules. The polymerizationprocess may utilize a monomer of styrene to form a polymer layer ofpolystyrene, for example. Polystyrene is a well-known vinyl polymerhaving a long hydrocarbon chain with a phenyl group attached to everyother carbon atom. As another example, the polymerization process mayuse a monomer which is methyl methacrylate (MMA) which forms a polymerlayer of poly(methyl methacrylate) (PMMA). However, any suitable monomermay be utilized to form any suitable polymer.

During the polymerization process, the structure of FIG. 14 is placedinto a conventional polymerization reactor which is filled with themonomer. Heat is applied in the reactor so that the polymer starter isactivated. A polymer chain grows on the surface until the desiredthickness is achieved (i.e. to form a substantially planar or coplanarsurface). Thus, the polymerization process is suitably timed so that aplanarized surface results. In the present embodiment, thepolymerization process may take from between 5 minutes and severalhours. When complete, the application of heat is stopped and the surfaceis washed to remove any free polymers.

The substantially planar surface as illustrated in FIG. 15 is therebyobtained. However, this surface may have very small remaining stepsbetween the materials, on the order of 5 nanometers (nm) for example.The substantially planar surface with eliminated or reduced-sized stepsis advantageous for subsequent processing steps (e.g. photolithographysteps). The thickness distribution of subsequently deposited materialswill be more uniform and surface scattering is less likely to occur.After the polymerization process, a seed layer is deposited over theplanar surface for a subsequent electroplating process. The seed layermay be made of a suitable metal or magnetic material, such asnickel-iron (NiFe). Contact (physical, electrical, and/or magneticcontact) between the seed layer and the tops of first materialstructures 1104 may thereby be achieved. The conventional electroplatingprocess may then be performed.

FIGS. 16–19 are cross-sectional views of partially constructed magneticheads for describing an alternative surface planarization method. Themethod of FIGS. 16–19 may be utilized for making a magnetic head in thedisk drive described above in relation to FIGS. 4–10. The method beginswith FIG. 16 which shows a partially constructed magnetic head 1600 madein the same manner as that described above in relation to FIG. 11. Theinitial structure 1600 includes a substrate 1602 having a plurality offirst material structures 1604 formed thereon. In this example, firstmaterial structures 1604 include structures 1606, 1608, and 1610. Sincestructures 1606, 1608, and 1610 cover only portions of substrate 1602,recesses (such as recesses 1612 and 1614) are formed between structures1606, 1608, and 1610 and the exposed portions of substrate 1602. In thefabrication of magnetic heads, substrate 1602 is typically a metaland/or a magnetic material (such as a pole piece layer of a magnetichead), whereas first material structures 1604 are typically a metaland/or a magnetic material (such as a pedestal of the pole piece). Themagnetic material may include nickel-iron (NiFe) or cobalt-iron (CoFe).

It is desired to fill in these recesses with a material (e.g. aninsulator) in an attempt to form a top planar surface with the tops ofstructures 1606, 1608, and 1610. This is done so that another material(e.g. a metal and/or a magnetic material) can be deposited over thesurface and contact can be made (i.e. physical, electrical, and/ormagnetic contact) with it and the tops of the first material structures1604.

To illustrate, it is shown in FIG. 17 that a second material 1702 isdeposited over and around these first material structures 1604. Secondmaterial 1702 may be an insulator, such as alumina (Al₂O₃). In FIG. 18,it is shown that a chemical mechanical polishing (CMP) is performed overthe structure to remove top surface portions of second material 1702such that the tops of first material structures 1604 are exposed and atop surface (which is somewhat flat) is formed from the tops of firstand second materials 1604 and 1702. However, small surface steps remainbetween first and second materials 1604 and 1702 along the top surfaceeven after the CMP (i.e., the resulting top surface is not entirelycoplanar). Steps remain between the materials because they havedifferent CMP removal rates. These surface steps may be, for example, inthe range of about 10–300 nm. If no other processes are utilized toreduce the size of these steps, the non-ideal situation adverselyaffects subsequent processing steps (e.g. photolithography steps) asdescribed earlier.

In FIG. 19, it is shown that polymer layers 1902 are selectively bondedover the tops of second materials 1802. The polymer layers are appliedby dipping the structure of FIG. 18 into a polymer solution that has aspecific headgroup that reacts with second materials 1802. Little or noabsorption or bonding occurs between the polymer and the top surfaces offirst material structures 1604. Preferably, polymer layers 1902 areformed to a thickness sufficient to reach the height of the tops ofsecond material structures 1604. That is, the process is preferablyemployed such that polymer layers 1902 and first material structures1604 form a substantially planar top surface. In the present embodiment,polymer layers 1902 have a thickness of between about 10–300 nmdepending on the exact materials utilized. The dipping or application isdone for a suitable time period to achieve the desired thickness, suchas between about 2 and 200 seconds. As apparent, this process isdifferent from that described in relation to FIGS. 11–15 in that thepolymerization occurs prior to the application to the structure. Thepolymer may be any suitable polymer, such as a modified polystyrene(e.g. a di-block copolymer). The resulting bond between the materialsmay be any suitable bond, such as a silane bond or a thiol bond.

The substantially planar surface as illustrated in FIG. 19 is therebyobtained. However, this surface may have very small remaining stepsbetween the materials, on the order of 1–5 nanometers (nm) (afterprocessing), for example. The substantially planar surface witheliminated or reduced-sized steps is advantageous for subsequentprocessing steps (e.g. photolithography steps). The thicknessdistribution of subsequently deposited materials is more uniform andsurface scattering is less likely to occur. After this polymer layersare applied, a seed layer is deposited over the planar surface for asubsequent electroplating process. The seed layer may be made of asuitable metal or magnetic material, such as nickel-iron (NiFe). Contact(physical, electrical, and/or magnetic contact) between the seed layerand the tops of first material structures 1104 is achieved. Theconventional electroplating process may then be performed.

FIGS. 20–22 are cross-sectional views of partially constructed magneticheads for describing another alternative inventive surface planarizationtechnique. The method of FIGS. 20–22 may be utilized for making amagnetic head in the disk drive described above in relation to FIGS.4–10. With the method of FIGS. 20–22, the CMP process described in themethods of FIGS. 11–15 and 16–19 is not needed. The method begins withFIG. 20 which shows a partially constructed magnetic head 2000 made inthe same manner as that described above in relation to FIG. 11. Theinitial substrate structure 2000 includes a first material substrate2002 having a plurality of second material structures 2004. In thisexample, second material structures 2004 include structures 2006, 2008,and 2010. Since structures 2006, 2008, and 2010, cover only portions offirst material substrate 2002, recesses (such as recesses 2012 and 2014)are formed between second material structures 2006, 2008, and 2010 andthe exposed portions of first material substrate 2002. In thefabrication of magnetic heads, first material substrate 2002 istypically an insulator, such as alumina (Al₂O₃), whereas second materialstructures 2004 are typically metal or magnetic, such as nickel-iron(NiFe) or cobalt-iron (CoFe).

In FIG. 21, it is shown that a polymer initiator layer 2102 (or polymerstarter) is applied and selectively absorbed only by the top surfaces offirst material substrate 2002 (i.e. the insulator). A chemical bond isformed between the tops of first material substrate 2002 and polymerinitiator layer 2102. In contrast, little or no absorption or bondingoccurs between the polymer initiator and the top surfaces of secondmaterial structures 2004. Polymer initiator layer 2102 may be, forexample, Azomonochlorsilane (AMCS) where a resulting silane bond isformed between the tops of first material substrate 2004 and polymerinitiator layer 2102. As another example, polymer initiator layer 2102may be Azo-Thiol Compound where a resulting thiol bond is formed betweenthe tops of first material substrate 2002 and polymer initiator layer2102. Polymer initiator layer 2102 may be a monomolecular layer having athickness of one to a few nanometers (nm). The polymer starter may beapplied to the structure by dipping or floating over.

In FIG. 22, it is shown that a polymerization process is utilized toform polymer layers 2202 over the tops of first material substrate 2002.Preferably, polymer layers 2202 are formed to a thickness sufficient toreach the height of the tops of second material structures 2004. Thatis, the process is preferably employed such that polymer layers 2202 andsecond material structures 2004 form a substantially planar top surface.In the present embodiment, polymer layers 2202 have a thickness ofbetween about 50 and 2000 nm. The polymerization process may use amonomer of styrene which forms a polymer layer made of polystyrene, forexample. As another example, the polymerization process may use amonomer of MMA to form a polymer layer of PMMA. However, any suitablemonomer may be utilized to form any suitable polymer.

During the polymerization process, the structure of FIG. 21 is placedinto a conventional polymerization reactor which is filled with asuitable monomer. Heat is applied in the reactor so that the polymerstarter is activated. A polymer chain grows on the surface until thedesired thickness is achieved (i.e. to form a substantially planar orcoplanar surface). Thus, the polymerization process is suitably timed sothat a planarized surface results. In the present embodiment, thepolymerization process may take between about 30 and 600 minutes. Whencomplete, the application of heat is stopped and the surface is washedto remove any free polymers.

A substantially planar surface as illustrated in FIG. 22 is therebyobtained. This surface may have very small remaining steps between thematerials, on the order of 1–5 nanometers (nm) for example. Thesubstantially planar surface having eliminated or reduced-sized steps isadvantageous for subsequent processing steps (e.g. photolithographysteps). The thickness distribution of subsequently deposited materialswill be more uniform and surface scattering is less likely to occur.After the polymerization process, a seed layer is deposited over theplanar surface for a subsequent electroplating process. The seed layermay be made of a suitable metal or magnetic material, such asnickel-iron (NiFe). Contact (physical, electrical, and/or magneticcontact) between the seed layer and the tops of second materialstructures 2004 is achieved. The conventional electroplating process maythen be performed.

Thus, surface planarization methods for the fabrication of magneticheads or other devices in order to achieve good critical dimension (CD)control have been described. In one illustrative embodiment, magneticstructures are formed over a substrate and insulator materials aredeposited over and around the magnetic structures. A chemical mechanicalpolishing (CMP) is performed to remove top portions of the insulatormaterials and to expose the tops of the magnetic structures such thatthe tops of the magnetic and insulator materials form a top surface. Dueto the different CMP removal rates of the materials, small surface“steps” remain between the different materials even after the CMP.According to the invention, polymer materials (e.g. polystyrene or PMMA)are formed to selectively bond with the top of the insulator materials.The polymer materials are formed to a thickness sufficient such that thetops of the polymer and magnetic materials form a substantially planartop surface. The polymer materials may be formed by applying a polymerinitiator layer to create a bond with the top of the insulator materialsand subsequently performing a polymerization process. Alternatively, thepolymer materials may be formed by applying a polymer solution to thestructure. Since surface steps between the different materials areeliminated or substantially reduced to form a substantially planar topsurface, good critical dimension (CD) control in photolithographyprocesses can be achieved.

Unique structures also result from the inventive processes, such as amagnetic head which has a pole piece made of a magnetic material; one ormore magnetic pedestals formed over the pole piece; an insulatormaterial formed over the pole piece adjacent the magnetic pedestals; andone or more polymer layers formed over tops of the insulator material toform a substantially planar top surface with the magnetic pedestals. Oneor more polymer initiator layers may be formed between the tops of theinsulator material and the one or more polymer layers. The one or morepolymer layers may be made of polystyrene or PMMA, as examples. Thisunique magnetic head may be included within a magnetic recording device,such as a disk drive, which further includes at least one rotatablemagnetic disk; a spindle supporting the at least one rotatable magneticdisk; a disk drive motor for rotating the at least one rotatablemagnetic disk; and a slider for supporting the magnetic head.

It is to be understood that the above is merely a description ofpreferred embodiments of the invention and that various changes,alterations, and variations may be made without departing from the truespirit and scope of the invention as set for in the appended claims. Forexample, although the methods were described in relation to thefabrication of a magnetic head, the surface planarization processes maybe utilized for the fabrication of other devices such as semiconductorICs. None of the terms or phrases in the specification and claims hasbeen given any special particular meaning different from the plainlanguage meaning to those skilled in the art, and therefore thespecification is not to be used to define terms in an unduly narrowsense.

1. A surface planarization method, comprising: providing a substratestructure with a non-planar top surface that is defined by top surfacesof first and second materials; and forming polymer layers whichselectively bond with the top surface of the first material such that atop surface of the polymer layers and the top surface of the secondmaterial form a substantially planar top surface for the substratestructure.
 2. The method of claim 1, further comprising: applying apolymer initiator which selectively bonds with the top surface of thefirst material; and performing a polymerization process to form thepolymer layers over the polymer initiator.
 3. The method of claim 1,further comprising: applying a polymer solution over the substratestructure to form the polymer layers.
 4. The method of claim 1, whereinthe act of providing the substrate structure comprises the further actsof: depositing the first material over and around the second material;and performing a chemical-mechanical polishing (CMP) such to form thenon-planar surface.
 5. The method of claim 1, wherein the first materialcomprises a dielectric and the second material comprises a metal.
 6. Themethod of claim 1, wherein the polymer layers comprise polystyrene. 7.The method of claim 1, wherein the polymer layers comprise poly(methylmethacrylate) or PMMA.
 8. A surface planarization method, comprising:forming a plurality of metal structures over a substrate; depositing aninsulator material over and around the metal structures; performing achemical-mechanical polishing (CMP) which forms a non-planar top surfacedefined by top surfaces of the metal structures and the insulatormaterial; and forming polymer layers which bond with the top surface ofthe insulator material such that a top surface of the polymer layers andthe top surface of the metal structures form a substantially planar topsurface.
 9. The method of claim 8, further comprising: applying apolymer initiator which forms bonds with the top surface of theinsulator material; and performing a polymerization process to form thepolymer layers over the polymer initiator.
 10. The method of claim 8,further comprising: applying a polymer solution to form the polymerlayers.
 11. The method of claim 8, further comprising: forming a seedlayer over the substantially planar top surface.
 12. The method of claim8, wherein the polymer layer comprises polystyrene.
 13. The method ofclaim 8, wherein the polymer layer comprises poly(methyl methacrylate)or PMMA.
 14. The method of claim 8, which is utilized for making amagnetic head.
 15. A surface planarization method, comprising: forming aplurality of metal structures over an insulator material; formingpolymer initiator layers which selectively bond with tops of theinsulator material; and performing a polymerization process to formpolymer layers having a thickness sufficient to form a substantiallyplanar top surface with tops of the metal structures.
 16. The method ofclaim 15, wherein the polymer layers comprise polystyrene.
 17. Themethod of claim 15, wherein the polymer layers comprise poly(methylmethacrylate) or PMMA.
 18. The method of claim 15, which is utilized formaking a magnetic head.